Chinchi, I'm not sure if you were being serious or not, but from experience I can say that chins can swim and don't 'just sink'. Yeah, they get drenched immediately, but their fur isn't really heavier in the water than any other fur or hair. Those with long hair may know that it isn't until you get out of the water that you feel the weight of wet hair.
The only issue with chin fur getting wet that I've come across is that it doesn't dry, at least not on it's own. If the owner doesn't take the proper steps to help the chin dry, the fur will just get all matted, stay wet, and the chin may end up with fungus or mold. I can see how a chin may panic and then drown though.
The stress of being immersed in water followed by matted, wet fur could also possibly lead to a weakened immune system causing more problems later on.
Having had two chins unintentionally jump into water over the years, I can say that they don't just sink, their fur doesn't fall out, they don't transform into evil gremlins, and it's not a huge problem if you immediately start towel drying and blow drying them off and minimizing stress as much as possible, while also trying to keep them cool. Blow drying on cool works best for drying off a chinchilla, but you have to stretch it out over a long period (taking breaks to prevent overheating as most dryers, even on cool, still blow out warmer air) and make sure that the fur is completely dry. A dust bath following the last blow drying session is usually greatly appreciated and helps ensure that the fur is dry.
For those that are curious, one of the wet chins got away while I was cleaning cages. She took a flying leap off of another chins cage and landed right in my bucket of bleach water. The bleach worried me more than anything, but she was fine. The other was a chin who escaped when I failed to latch a cage properly. She ended up in a tub full of water. Again, she was fine after careful drying. Both chins were scared at first, but were back to their normal selves before they were even fully dried off.